The present inventive subject matter relates generally to the art of radio frequency (RF) communications and/or other like wireless or over-the-air (OTA) telecommunications. Particular relevance is found in connection with crates or other containers or the like that bear RFID (RF IDentification) devices or other similar telecommunication devices, and accordingly the present specification makes specific reference thereto. However, it is to be appreciated that aspects of the present inventive subject matter are also equally amenable to other like applications.
RFID devices are generally known in the art. Conventionally, RFID receivers, transmitters and/or transponders (collectively referred to herein as RFID “devices”) are widely used to associate a tagged or labeled object with an identification code and/or other information provided by the RFID device. RFID devices are conventionally used, e.g., to track inventory, parcels and/or other objects.
A typical RFID device generally includes a number of components including an antenna for wirelessly transmitting and/or receiving RF signals and analog and/or digital electronics operatively connected thereto. So called active or semi-passive RFID devices may also include a battery, capacitor, super capacitor or other suitable power source. In conventional parlance, the RFID electronics along with any operatively connected antenna and/or power source are collectively referred to as the RFID inlay. Exemplary RFID inlays are available from Avery Dennison RFID Company of Clinton, S.C. Commonly, the electronics are implemented via an integrated circuit (IC) or microchip or other suitable electronic circuit and may include, e.g., communications electronics, data memory, control logic, etc. In operation, the IC or microchip functions to store and/or process information, modulate and/or demodulate RF signals, as well as optionally performing other specialized functions. In general, RFID devices can typical retain and communicate enough information to uniquely identify individuals, packages, inventory and/or other like objects, e.g., to which the RFID device is affixed.
Commonly, an RFID reader or base station is used to wirelessly obtain data or information (e.g., such as the aforementioned identification code) communicated from an RFID device. The manner in which the RFID reader interacts and/or communicates with the RFID device generally depends on the type of RFID device. A given RFID device is typically categorized as a passive device, an active device, a semi-passive device (also known as a battery-assisted or semi-active device) or a beacon type RFID device (which can be thought of as a sub-category of active devices). Passive RFID devices generally use no internal power source, and as such, they are passive devices which are only active when an RFID reader is nearby to power the RFID device, e.g., via wireless illumination of the RFID device with an RF signal and/or electromagnetic energy from the RFID reader. Conversely, semi-passive and active RFID devices are provided with their own power source (e.g., such as a small battery). To communicate, conventional RFID devices (other than so called beacon types) respond to queries or interrogations received from RFID readers. The response is typically achieved by backscattering, load modulation and/or other like techniques that are used to manipulate the RFID reader's field. Commonly, backscatter is used in far-field applications (i.e., where the distance between the RFID device and reader is greater than approximately a few wavelengths), and alternately, load modulation is used in near-field applications (i.e., where the distance between the RFID device and reader is within approximately a few wavelengths).
Passive RFID devices typically signal or communicate their respective data or information by backscattering a carrier wave from an RFID reader. That is to say, in the case of conventional passive RFID devices, in order to retrieve information therefrom, the RFID reader typically sends an excitation signal to the RFID device. The excitation signal energizes the RFID device which transmits the information stored therein back to the RFID reader. In turn, the RFID reader receives and decodes the information from the RFID device.
As mentioned earlier, passive RFID devices commonly have no internal power supply. Rather, power for operation of a passive RFID device is provided by the energy in the incoming RF signal received by the RFID device from the RFID reader. Generally, a small electrical current induced in the antenna of the RFID device by the incoming RF signal provides just enough power for the IC or microchip in the RFID device to power up and transmit a response. This means that the antenna generally has to be designed both to collect power from the incoming signal and also to transmit the outbound backscatter signal.
Passive RFID devices have the advantage of simplicity and long life (e.g., having no battery to go dead). Nevertheless, their performance may be limited. For example, passive RFID devices generally have a more limited range as compared to active RFID devices.
Active RFID devices, as opposed to passive ones, are generally provisioned with their own transmitter and a power source (e.g., a battery, photovoltaic cell, etc.). In essence, an active RFID device employs the self-powered transmitter to broadcast a signal which communicates the information stored on the IC or microchip in the RFID device. Commonly, an active RFID device will also use the power source to power the IC or microchip employed therein.
Broadly speaking, there are two kinds of active RFID devices—one that can be generally thought of as a transponder type of active RFID device and the other as a beacon type of active RFID device. A significant difference is that active transponder type RFID devices are only woken up when they receive a signal from an RFID reader. The transponder type RFID device, in response to the inquiry signal from the RFID reader, then broadcasts its information to the reader. As can be appreciated, this type of active RFID device conserves battery life by having the device broadcast its signal only when it is within range of a reader. Conversely, beacon type RFID devices transmit their identification code and/or other data or information autonomously (e.g., at defined intervals or periodically or otherwise) and do not respond to a specific interrogation from a reader.
Generally, active RFID devices, due to their on-board power supply, may transmit at higher power levels (e.g., as compared to passive devices), allowing them to be more robust in various operating environments. However, the battery or other on-board power supply can tend to cause active RFID devices to be relatively larger and/or more expensive to manufacture (e.g., as compared to passive devices). Additionally, as compared to passive RFID devices, active RFID devices have a potentially more limited shelf life—i.e., due to the limited lifespan of the battery. Nevertheless, the self supported power supply commonly permits active RFID devices to include generally larger memories as compared to passive devices, and in some instances the on-board power source also allows the active device to include additional functionality, e.g., such as obtaining and/or storing environmental data from a suitable sensor.
Semi-passive RFID devices are similar to active devices in that they are typically provisioned with their own power source, but the battery commonly only powers the IC or microchip and does not provide power for signal broadcasting. Rather, like passive RFID devices, the response from the semi-passive RFID device is usually powered by means of backscattering the RF energy received from the RFID reader, i.e., the energy is reflected back to the reader as with passive devices. In a semi-passive RFID device, the battery also commonly serves as a power source for data storage.
A conventional RFID device will often operate in one of a variety of frequency ranges including, e.g., a low frequency (LF) range (i.e., from approximately 30 kHz to approximately 300 kHz), a high frequency (HF) range (i.e., from approximately 3 MHz to approximately 30 MHz) and an ultra-high frequency (UHF) range (i.e., from approximately 300 MHz to approximately 3 GHz). A passive device will commonly operate in any one of the aforementioned frequency ranges. In particular, for passive devices: LF systems commonly operate at around 124 kHz, 125 kHz or 135 kHz; HF systems commonly operate at around 13.56 MHz; and, UHF systems commonly use a band anywhere from 860 MHz to 960 MHz. Alternately, some passive device systems also use 2.45 GHz and other areas of the radio spectrum. Active RFID devices typically operate at around 455 MHz, 2.45 GHz, or 5.8 GHz. Often, semi-passive devices use a frequency around 2.4 GHz.
The read range of an RFID device (i.e., the range at which the RFID reader can communicate with the RFID device) is generally determined by many factors, e.g., the type of device (i.e., active, passive, etc.). Typically, passive LF RFID devices (also referred to as LFID or Low Frequency devices) can usually be read from within approximately 12 inches (0.33 meters); passive HF RFID devices (also referred to as HFID or High Frequency devices) can usually be read from up to approximately 3 feet (1 meter); and passive UHF RFID devices (also referred to as Ultra high frequency devices) can be typically read from approximately 10 feet (3.05 meters) or more. One important factor influencing the read range for passive RFID devices is the method used to transmit data from the device to the reader, i.e., the coupling mode between the device and the reader—which can typically be either inductive coupling or radiative/propagation coupling. Passive LFID devices and passive HFID devices commonly use inductive coupling between the device and the reader, whereas passive UHF RFID devices commonly use radiative or propagation coupling between the device and the reader.
In inductive coupling applications (e.g., as are conventionally used by passive LF RFID and HF RFID devices), the device and reader are typically each provisioned with a coil antenna that together form an electromagnetic field therebetween. In inductive coupling applications, the device draws power from the field, uses the power to run the circuitry on the device's IC or microchip and then changes the electric load on the device antenna. Consequently, the reader antenna senses the change or changes in the electromagnetic field and converts these changes into data that is understood by the reader or adjunct computer. Because the coil in the device antenna and the coil in the reader antenna have to form an electromagnetic field therebetween in order to complete the inductive coupling between the device and the reader, the device often has to be fairly close to the reader antenna, which therefore tends to limit the read range of these systems.
Alternately, in radiative or propagation coupling applications (e.g., as are conventionally used by passive UHF RFID devices), rather than forming an electromagnetic field between the respective antennas of the reader and device, the reader emits electromagnetic energy which illuminates the device. In turn, the device gathers the energy from the reader via its antenna, and the device's IC or microchip uses the gathered energy to change the load on the device antenna and reflect back an altered signal, i.e., backscatter. Commonly, UHF RFID devices can communicate data in a variety of different ways, e.g., they can increase the amplitude of the reflected wave sent back to the reader (i.e., amplitude shift keying), shift the reflected wave so it's out of phase with respect to the received wave (i.e., phase shift keying) or change the frequency of the reflected wave (i.e., frequency shift keying). In any event, the reader picks up the backscattered signal and converts the altered wave into data that is understood by the reader or adjunct computer.
The antenna employed in an RFID device is also commonly affected by numerous factor, e.g., the intended application, the type of device (i.e., active, passive, semi-active, etc.), the desired read range, the device-to-reader coupling mode, the frequency of operation of the device, etc. For example, insomuch as passive LF RFID devices are normally inductively coupled with the reader, and because the voltage induced in the device antenna is proportional to the operating frequency of the device, passive LF RFID devices are typically provisioned with a coil antenna having many turns in order to produce enough voltage to operate the device's IC or microchip. Comparatively, a conventional HF RFID passive device will often be provisioned with an antenna which is a planar spiral (e.g., with 5 to 7 turns over a credit-card-sized form factor), which can usually provide read ranges on the order of tens of centimeters. Commonly, HF RFID antenna coils can be less costly to produce (e.g., compared to LF RFID antenna coils), since they can be made using techniques relatively cheaper than wire winding, e.g., lithography or the like. UHF RFID passive devices are usually radiatively and/or propagationally coupled with the reader antenna and consequently can often employ conventional dipole-like antennas.
Using an RFID device to track and/or identify an object or inventory is not unknown in general. However, limitations of conventional RFID devices can be experienced in some circumstances. In particular, exchanging RF signals between an RFID device and reader can be complicated by certain substances that are generally “RF unfriendly,” e.g., such as water or metal. These RF unfriendly materials can block or impede RF signals or act to detune the respective antenna of an RFID device in close proximity to the material.
For example, the foregoing phenomena can be especially problematic when a plurality of crates or other containers of RF unfriendly material are stacked together, e.g., on a pallet or otherwise. With reference now to FIG. 1, such an arrangement is shown. More specifically, crates 10a through 10d are shown stacked together in close proximity to one another. For the sake of illustrating the present point, each crate contains an RF unfriendly material, e.g., one or more bottles of water 12. Additionally, each crate is tagged on one side thereof with an RFID device or inlay 14a through 14d. As can be appreciated, when the crates are positioned together next to one another (e.g., such that their relative orientation to one another is random or quasi-random), it is possible that one or more of the RFID inlays (e.g., inlays 14c and 14d in the illustrated example) will be positioned on a wall or side of its respective crate that resides on the interior of the overall stack. Accordingly, an RFID reader (e.g., such as the illustrated reader 20) at the periphery of the overall stack may have trouble communicating with the buried inlays.
Of course, one solution to the forgoing problem is to deliberately stack and/or position the crates such that the RFID inlays always reside on walls or sides of the respective crates that face an exterior perimeter of the overall stack. However, manual execution of this solution can be labor intensive and/or prone to human error. Mechanical and/or automatic implementation of the this solution on the other hand involves additional equipment to detect which side of each crate bears the RFID inlay and then control or adjust each crate's relative orientation accordingly.
Therefore, a new and/or improved approach and/or crate is disclosed which addresses the above-referenced problem(s) and/or others.